The present invention relates to a sync signal generator and, more particularly, to a sync signal generator of a television receiver which is installed in a vehicle and can also provide a good video image even when a video signal is received while the vehicle is moving.
Hitherto, as a television receiver for use in a vehicle, a receiver disclosed in JP-A-61-70878 (laid open on Apr. 11, 1986) has been known as an example. The television receiver of the above conventional example comprises: four diversity antennas installed to a moving object; a switching circuit for switching so as to connect either one of outputs of the four antennas to an antenna input circuit of a television receiver installed in the moving object; and a controller for time-sharingly switching the switching circuit by a sampling switching control signal which is generated within a vertical blanking period of a television video signal, for comparing levels of the detection outputs of the antennas, for allowing the antenna having the highest level to be connected to the antenna input circuit of the television receiver, and for holding such a state until a next vertical blanking period, wherein the optimum receiving state is always held even if the reception environment is changed by the movement of the vehicle.
However, in the conventional technique, no consideration is made to a point of stabilization of synchronism and there is a problem such that a reception image is deteriorated by a large sync fluctuation which is caused by a ghost phenomenon, a fading phenomenon, and the like which occur due to influences by waves which are reflected by a building or the like during running.
It is an object of the invention to solve the problems of the conventional technique and to provide a sync signal generator which can obtain both of stable horizontal and vertical sync signals even during the running of a vehicle.